Automated Transfer Vehicle

Comparison of the ATV, Progress capsule,
and Apollo Command and Service Modules. Credit: ESA

An unmanned spacecraft developed by the European Space Agency
(ESA) to supply the International Space Station
with food, water, fuel, and experimental equipment. In addition, ATVs are
able to re-boost the ISS whose 300km-plus orbit tends to shrink over time
due to friction with the atmosphere.

Each ATV is launched by an Ariane 5 from
Kourou, French Guiana. After approximately two days of flight it arrives
at the ISS and docks automatically to the Russian Service Module Zvezda.
The first launch of an ATV (Jules verne) took place on March 9, 2008.

As big as a double-decker bus and with a mass at launch of almost 20 metric
tons, the ATV is the biggest and most complex spacecraft Europe has ever
flown. It is also the largest spacecraft capable of automatic rendezvous
and docking.

Design

The ATV has three times the capacity of the Russian Progress
spacecraft, which it is designed to complement. Like the Progress, it carries
both bulk liquids and relatively fragile freight which is stored in a cargo
hold kept in a pressurized shirtsleeve environment so that astronauts can
have access to it without putting on a spacesuit.

Each ATV weighs 20.7 metric tons at launch and has a cargo capacity of 9
metric tons, including:

Up to 100 kg of gas (nitrogen, oxygen, air), with up
to two gases per flight

Up to 4700 kg of propellant for refueling and re-boosting
the station.

Journey to the space station

The shroud around the ATV separates
as it reaches orbit

Approaching the International Space
Station

Optical sensors guiding the docking
maneuver

The ATV is delivered by its Ariane launch vehicle into a
230km-high (140 miles) orbit, underneath the ISS. It then uses its own engines
to raise its height and edge closer and closer to the space station over
a series of orbits. The ATV's onboard computers are in charge of maneuvers.
In the latter stages, optical sensors guide the ATV into position on the
end of the Russian Zvezda module. Although both ATV and ISS are moving relative
to the Earth's surface at some 27,000km/h (17,000mph), they lock together
at less than walking pace. Once the ATV is securely docked, the station
crew can start to unpack.

The crew enter the pressurized part of the ATV. This is similar in layout
to the Italian-built cargo modules, known as Multi-Purpose
Logistics Modules, which are taken to the ISS by the Space Shuttle to
deliver consumables, equipment, and tools. Oxygen brought up by the ATV
is vented directly into the station, water is carried out in bags, and fuel
is piped across to Zvezda. An ATV stays at the ISS for about six months.
At intervals of 10 to 45 days, the ATV's thrusters are used to boost the
station's altitude.

Over time, the station crew use the vehicle as a refuse skip, filling the
cargo section with up to 6.4 metric tons of waste. After undocking, the
ATV destroys all this material, and itself, in a controlled re-entry and
burn-up over the Pacific Ocean.

The first ATV – dubbed "Jules Verne" – was launched atop a specially
prepared Ariane 5 in March 2008. Four others are currently planned.

Future possibilities

On the design board now is a re-entry capsule that would be jettisoned by
a returning ATV prior to the vehicle's destruction in the atmosphere. The
capsule would land safely any experimental items from the ISS that were
required for further study in Earth labs.

Another possibility is that ATVs could be given a more open architecture.
This would overcome the approximately 80cm-width (30 inches) restriction
placed on ATV packages by the size of the hatch. If the vehicle were made
with no side walls, larger components such as batteries and gyros could
be delivered to the station. Spacewalking astronauts could then maneuver
these bulkier items into place with the help of the station's robotic arm.
Although the ATV is not currently designed to carry astronauts the fact
that it has a pressurized compartment inside which people can move around
safely demonstrates that an ATV-based human transportation system could
eventually be developed.